Powertrain, generic (extended)

P2D45 Reductant Temperature Too Low

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P2D45 means the diesel exhaust fluid in the tank does not warm up as it should while the tank heater is working, so frozen or very cold fluid cannot be dosed. GM uses the code in its diesel OBD tables from 2021 to 2025 in two variants. In the separate reductant control module, after over 28,800 s engine-off, with fluid between -40 and -14 °C, more than 5 L in the tank and a heater command of at least 10 W, the module compares the measured mean temperature with what a just-acceptable heater would reach; staying below it fails the test, judged once per trip on a 600 s basis. A 2023 engine module variant checks that the tank warms from a start below 0 °C. Both are Type B. Heater circuit faults: P20B9 ff.; too hot: P24FF.

Likely causes

Tank heater element degraded or partly failed
Low supply voltage to the heater, e.g. weak battery or poor ground
Tank temperature sensor reading too low

Symptoms

  • MIL after two trips in cold weather
  • DEF or SCR warning message, dosing delayed
  • Possible countdown to speed limitation if the fault persists

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€100–1,500
Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

reductant tankreductant tank heaterreductant tank temperature sensor

Related codes

P24FFP20B9P205AP2042

References: gsi.ext.gm.com, gsi.ext.gm.com, law.cornell.edu.